This invention relates to an apparatus for closing a fireproof door, normally locked in its open position, in case of emergency such as fire either by remote-controlled energization of a solenoid or man-controlled closing force.
In the prior closing apparatus, a slider normally latched by a latch mechanism is released by remote-controlled energization of a solenoid in case of fire and the fireproof door is automatically closed by, for instance, a door closer. It is desired, however, to manually release a slider from a latch mechanism so as to close the fireproof door by man-controlled manipulation, thereby assuring a reliable unlocking even when a solenoid is in trouble.
Further, in the prior closing apparatus, latching force of the latch mechanism is normally set to a level higher than necessary to avoid a slider to be unintentionally released. However, it is desired, also, to make it possible to adjust the latching force of the latch mechanism since manual closing becomes difficult when the latching force is excessive.
In order to overcome the above defects of the prior apparatuses, an improved closing apparatus has been proposed in the U.S. patent application Ser. No. 645,921. In this apparatus, the latch mechanism comprises an actuator plate which is spring-loaded and floatably supported on an adjusting screw adapted to adjust a resilient force of a spring and is swingable around a fulcrum shaft. The slider is provided with a hook portion at the front end thereof to engage a support pin mounted at the rear end of the actuator plate.
With this apparatus, besides remote-controlled energization of a solenoid, the slider can be released from the actuator plate by transmitting a manual door closing force onto the slider as the backward sliding force therefor, provided that the backward sliding force is larger than the resilient force of the spring.
Further, as described above, the resilient force of the spring can be suitably adjusted by the adjusting screw. Thus, the defects of the prior closing apparatus have been overcome.
The above apparatus, however, as the actuator plate itself is spring-loaded and floatably supported on the adjusting screw, the actuator plate and the related parts thereof have larger-scale and complex constructions. Further, the swing operation of the actuator plate becomes not-sufficiently accurate, which causes malfunction of the closing apparatus.